invertebrates: phylum porifera

Invertebrates: Phylum PoriferaSponges

Multicellular; body a loose aggregate of cells

All aquatic, mostly marineBody with pores (ostia), canals, and chambers

for circulation of water◦ Epidermis of flat cells, some with contractile fibers◦ Middle layer is semi-fluid, with wandering

amebocytes◦ Inner layer of choanocytes-flagellated to move

water

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Phylum Porifera cont’dFilter feeders- intracellular digestion

◦Cells get food from circulating water

Classified based on skeleton◦Composed of spicules

Chalk sponges - spicules of calcium carbonate Glass sponges - spicules of silica Proteinaceous sponges - spongin fibers

Reproduction◦asexual by budding, sexual by fusion of gametes

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Sponge

Fig. 30.3 30-3

Invertebrates: Phylum CnidariaCnidarians

◦Multicellular, tubular or bell-shaped animals-radial symmetry

◦All aquatic, mostly marine2 germ layers during

development◦Organized at tissue level

Nematocysts◦stinging cells unique to cnidarians

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Cnidarians cont’d2 body types-polyps and medusae

◦Life cycle alternates between both forms in some; in others one form is reduced or absent

Gastrovascular cavity-sac-like body plan

Includes corals, jellyfish, and hydrozoans◦Corals- polyps◦ Jellyfish-medusae◦Hydrozoans-may have both forms

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Cnidarian diversity

Fig. 30.4

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Cnidarians cont’dHydra

◦Representative organism (Class Hydrozoa)

◦Freshwater, attaches to rocks, leaf litter

◦Small tubular polyp, sac-like body plan with a single opening Outer tissue layer – epidermis from

ectoderm Inner layer – gastrodermis from

endoderm Longitudinal and circular muscle fibers

present Diffuse nerve net between layers

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Cnidarians cont’d◦Digestion begins in gastrovascular

cavity, completed in cells◦Can reproduce sexually and

asexually (budding) Sexual reproduction- hydra develops an

ovary or testis in body wall-produces gametes

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Anatomy of Hydra

Fig. 30.5 30-9

Invertebrates: Phylum PlatyhelminthesFlatwormsBilateral symmetry, three germ

layers, acoelomateMesoderm gives greater

complexity◦Muscles, excretory, reproductive,

and digestive systems in some◦Respiration by diffusion and

circulation

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Platyhelminthes cont’dClass Turbellaria - Planarians

◦Free-living flatworms

◦freshwater, feed on small living and dead organisms

◦Ladder-like nervous system Ganglia and eyespots anterior Auricles – chemosensitive receptores

◦Digestion: Feed through muscular pharynx Specialized cells for excretion: flame cells

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Platyhelminthes cont’dClass Turbellaria - Planarians

cont’d

◦3 muscle layers- circular, longitudinal, and diagonal Allows for more complex movements

◦Cephalization Organized to have an anterior end and a

posterior end

◦Hermaphroditic 30-12

Planarian

Fig. 30.6 30-13

Parasitic PlatyhelminthesClass Cestoda (Tapeworms)

◦Internal parasites as adults◦Body Structure

Tegument: tough outer covering protect from host’s enzymes

Scolex - head Barbs/hooks for attachment

Proglottids: segments Each contains organs of both sexes

◦Lack a digestive system- why?

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Parasitic Platyhelminthes cont’dClass Cestoda (Tapeworms) (cont’d)

◦Reproduction Fertilization is internal

proglottids filled with fertilized eggs are called gravid Gravid proglottids drop off and pass out in feces

Ingested by intermediate host larvae become encysted

Intermediate host is then eaten by definitive host Larvae mature to adults

◦Representative Organism: Tanea solium Pork tapeworm

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Life cycle of a tapeworm, Taenia

Fig. 30.7 30-16

Parasitic Platyhelminthes cont’d

Class Trematoda - Flukes◦Endoparasites of many species

◦Body Structure Tegument Oral sucker and posterior sucker

◦Digestion Well-developed digestive canal

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Parasitic Platyhelminthes cont’d

Class Trematoda - Flukes cont’d

◦Muscles and excretory system much like free-living flatworms Poorly developed sense organs- why

might that be?

◦Reproduction Hermaphroditic Complex life cycle involving two

intermediate hosts

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Parasitic Platyhelminthes cont’d

Class Trematoda - Flukes cont’d

◦Representative Organism: Clonorchis sinensis Liver Fluke Transmission

Snails ingest eggs Develop in to larvae, which leave the snail and

burrow into muscles of a fish Humans ingest fish

Larvae moves into bile ducts where adults develop

Eggs pass out of human in feces, cycle continues

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Invertebrates: Phylum NematodaRoundworms

◦First appearance of Tube-within-a-tube body plan

2 openings, mouth and anus Body Cavity

Pseudocoelomates Pseudocoel -filled with fluid, acts as

hydrostatic skeleton

◦Many species; some are free-living in soil and water, others are parasitic

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Coelom structure and function

Fig. 30.8 30-21

Parasitic NematodesAscaris

◦Move with whip-like motion◦Intestinal parasites in many animal species◦Females are much longer than males and

highly prolific◦Eggs enter host in uncooked vegetables,

soil, or feces Larvae burrow out of intestine and migrate to

heart and lungs Larvae are coughed up and swallowed Mature to adults in intestines

Estimated to infect 25% of world population

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Roundworm anatomy

Fig. 30.9 30-23

Parasitic Nematodes cont’dTrichinella spiralis

◦the trichina worm◦Causes trichinosis◦Humans contract the worm by eating

undercooked pork◦Larvae migrate out of intestines and

form painful cysts in the muscles

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Parasitic Nematodes cont’d

Wuchereria bancrofti◦ filarial worm that

causes elephantiasis

◦ Migrates into lymphatic vessels and prevents lymph drainage

◦ Edema occurs

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Parasitic Nematodes cont’d

Pinworms and hookworms◦Roundworm parasites which cause

problems in children◦Much more common in U.S.

Pinworms are primarily an annoyance Hookworms cause skin irritations and in

some cases debilitating disease

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